The present project is directed to the study of the role of proteins of the complement and of the coagulation system in monocyte and macrophage migration, localization at sites of inflammation and immune responses, and macrophage differentiation. It is based on previous work of the applicant and of othes which indicated that (a) complement activation generates peptides that induce macrophage chemotaxis (C5a), and spreading inducers that inhibit macrophage migration (Bb); (b) activation of the contract phase of blood coagulation inhibit macrophage migration; (c) monocytes have a plasma membrane receptor for fibronectin which promotes their attachment to collagen and fibrin; (d) binding to fibronectin receptors enhances the expression of receptors for Fc of IgG and for C3. The project proposes to further these studies in three major areas: I. To characterize the monocyte-fibronectin interaction; II. To establish the role of complement and coagulation derived peptides on monocyte and macrophage differentiation; III. To study the relationship between monocyte and macrophage adhesion to substrates with their subsequent functional behavior. These studies will employ human peripheral blood monocytes and mouse macrophages and will be performed mostly in "in vitro" systems. A number of monoclonal antibodies have been prepared for these studies including: three directed to human monocyte Fc receptors, two directed to the human monocyte receptor for fibronectin; and thirty one directed to different sites of the fibronectin molecule. These reagents, plus other techniques, will allow us to characterize the nature of molecular interactions of macrophages with their substrate, to analyze biochemical and functional markers of macrophage differentiation induced by the plamsa proteins, to isolate the receptor for fibronectin, and to study the expression of phagocytic, receptors induced by fibronectin. It is hoped that these experiments will generate information regarding the sequence of events that promote appropriate localization of monocytes in inflammatory sites and in sites of immune-reactions, and the identification of inducers of monocyte differentiation and activation. This knowledge could be important in the management of infectious processes and in approaches to the immunotherapy of tumors.